At Kahuna, copper-cobalt-gold mineralisation is developed along, and sub-parallel to, the sheared and altered contact between Palaeozoic metamorphic rock and a diorite intrusive. The contact follows the trend of the regional geology, coincides with a major lineament which extends for some 100 km to the north and is associated with several mines and numerous old workings. In the Kahuna area, the contact zone is commonly 50 m to 200 m wide, extends over 2 km and is strongly altered with carbonate and silicification. A series of mineralised quartz veins are developed along the contact.
A second series of veins diverge from the contact and can be traced eastwards into the historic Carrizal Alto area - an old mining area with many old shafts and open workings some of which exceed 500 metres in depth. Over 7 million tonnes were mined during the last century and up to the late 1940s. The mines are reported to have worked veins up to 15 metres wide - extracting high-grade copper and gold mineralisation with grades in excess of 8% copper, 1.5 g/t gold and 3.5 kg/t cobalt. Mining ceased when the workings at the 300 m level were flooded.
Previous work includes extensive regional and local geological reconnaissance mapping, a surface geochemical sampling programme and two phases of R.C. drilling, totalling almost 7,000 m. Other work completed includes: petrological studies, topographical surveying and the preparation of an environmental impact study.
Two geophysical surveys have been completed and confirm the lateral extension of the Carrizal Alto mineralised structures into the Kahuna area.
The reported production from Carrizal Alto, the results from the reconnaissance-scale reverse circulation in terms of grades and widths of mineralisation and the extensive development of areas with anomalous soil geochemistry indicate a high potential to develop multi-metal copper, cobalt and gold resources along the Kahuna shear zone and related fractures. The known mineralisation is open at depth and along strike.
